A document included in the trove of National Security Agency files released with Glenn Greenwald’s book No Place to Hide details how the agency’s Tailored Access Operations (TAO) unit and other NSA employees intercept servers, routers, and other network gear being shipped to organizations targeted for surveillance and install covert implant firmware onto them before they’re delivered.

These Trojan horse systems were described by an NSA manager as being “some of the most productive operations in TAO because they pre-position access points into hard target networks around the world.”